Actually, I don't understand how a species emerges. When a new species emerges, does it come from two parents? Does it emerge from a handful of individuals? For example, I know it's not this simple but say a raptor changes into a bird. Do two birds happen to be born and then they reproduce, or are ten birds randomly born and they find each other and reproduce. I am wondering if the homo sapiens come from two original parents or from a group of people?

jsfarney wrote:Actually, I don't understand how a species emerges. When a new species emerges, does it come from two parents? Does it emerge from a handful of individuals? For example, I know it's not this simple but say a raptor changes into a bird. Do two birds happen to be born and then they reproduce, or are ten birds randomly born and they find each other and reproduce. I am wondering if the homo sapiens come from two original parents or from a group of people?

Populations evolve, not individuals. Therefore, you have hundreds or thousands of individuals "staring" a new species. I put "starting" in quotes, because there is no set line between a mother species and a daughter species. It does not happen suddenly, even when an isolating mechanism evolves (like changes in mating behavior). Think of an anology: How many first Frechmen were there? Or first Italians?

LOL - the chicken and the egg problem. The egg came first. Suppose you have a way to decide whether an organism is human or not. Then, once upon a time, a the first human child was born to two non-human parents. But the child was practically certainly born from parents who were members of a population that were on the verge of becoming human. So maybe that child died before sexual maturity, with no offspring. Then a second human child was born from that population. Maybe the child had children with a non-human member of the population, and none of their descendants were human. Or maybe some were. Maybe other children were born from non-human parents. As the number of humans increased by these occurrences, maybe some human children were born from a mixed "marriage". There are many different possibilities, but eventually, the genetic advantage of being human resulted in an increase in the fraction of humans in the population.

The bottom line is that, assuming you can certainly decide whether an organism is human or not, the first human was born from two non-human parents, but it is possible that none of us, part of us, or all of us are decended from that first human.

What I have never quite understood is that we are taught that spontaneous mutations led to evolution - but when Rap's theory is right (and it certainly does sound reasonable to me) doesn't that mean that these mutations happened in more than one indvidual at a time and therefore making these mutations not-so-spontaneous? Maybe there was something around inducing these changes in more than one being at a time?

If you have a population on the verge of becoming human, then many of the members of that population are only 1, 2, a few mutations away from being human. That means that random mutations are more likely to produce a human from this population than to produce a human from a chimpanzee population. A chimpanzee population has many many mutations to be made before becoming human. A population on the verge of becoming human only needs a few, and so random mutations are more likely to produce a human. Also, sexual reproduction can produce never-before-seen organisms. If two mutations are needed to become human and one parent has one, the other the other, then the child could have both and qualify as a human, while neither of its parents were human, and no mutation occurred in the production of that child.

To answer the question as stated, yes, the first human being (however one defines that) had two parents. Our immediate ancestors on the hominid line reproduced sexually just as all primates do. Monkeys and apes all have two parents, all individuals of H. erectus had two parents each, and so did the first H. sapiens.

jsfarney wrote:Actually, I don't understand how a species emerges. When a new species emerges, does it come from two parents? Does it emerge from a handful of individuals? For example, I know it's not this simple but say a raptor changes into a bird. Do two birds happen to be born and then they reproduce, or are ten birds randomly born and they find each other and reproduce. I am wondering if the homo sapiens come from two original parents or from a group of people?

Populations evolve, not individuals. Therefore, you have hundreds or thousands of individuals "staring" a new species. I put "starting" in quotes, because there is no set line between a mother species and a daughter species. It does not happen suddenly, even when an isolating mechanism evolves (like changes in mating behavior). Think of an anology: How many first Frechmen were there? Or first Italians?

I really appreciate the thread author's general line of enquiry; they are a good kind of question, because the necessary definitions and clarifications help with the same conceptual kinds of problems when discussing "transitional" fossils. "transitional" in which way ? As an ancestral species between ancestral species ? Transitional in "shape" ?

robsabba, In your estimation, what requirements ( number of members, genetic variance in the group, or other parameters ) are to be met, in order for an individual or a group of individuals, to qualify as a "population" ? What restrictions exist ? Can an individual bacterium be a population ? Can a litter of puppies be a population ?